Engine thermostat having bypass pressure-dampening fluid passage

ABSTRACT

A thermostat assembly ( 200 ) includes an actuator portion ( 106 ) having a sealed container ( 126 ) with an arm ( 108 ) protruding therefrom. A retainer plate ( 118 ) connects the thermostat assembly ( 200 ) to an engine component ( 104 ). A bypass valve plate ( 228 ) is arranged to sealably engage a bypass valve seat ( 134 ) that is formed in another component ( 102 ). The bypass valve plate ( 228 ) includes a body portion ( 402 ) having a central opening ( 408 ) and an outer periphery, an inner rim ( 406 ) surrounds the central opening ( 408 ), an outer rim ( 404 ) surrounds the outer periphery, and a plurality of openings ( 230 ) are formed in the body portion ( 402 ). The plurality of openings ( 230 ) is adjacent to an interface between the body portion ( 402 ) and the outer rim ( 404 ), such that a bypass pressure-dampening fluid passage is defined through the plurality of openings ( 230 ) in the bypass valve plate ( 228 ).

FIELD OF THE INVENTION

This invention relates to internal combustion engines, including but not limited to control of an engine cooling system flow with a thermostat device.

BACKGROUND OF THE INVENTION

Internal combustion engines have cooling systems associated therewith that transfer heat away from the engine structure. These cooling systems typically include thermally actuated devices, or thermostats, that can route a cooling fluid flow either into the engine or into a radiator depending on a temperature of the cooling flow.

Typical engine thermostats are 3-way valves having one inlet and two outlets. A first port thereof acts as an inlet for the cooling fluid flow. A second port thereof acting as a first outlet, when open, directs the cooling fluid flow directly into the engine when the cooling flow is at a low temperature. A third port thereof acting as a second outlet, when open, allows the cooling fluid flow to bypass the engine and pass through a radiator, where it is cooled, before returning to the engine. A thermal actuator controls the opening of valves that control the cooling fluid flow into the first and/or second outlet. The thermal actuator, typically a material pushing onto a rod when heated and expanding, is immersed in the incoming cooling fluid flow at the inlet of the thermostat.

When an engine operates at high engine speed conditions, a cooling fluid flow rate is increased. This increased flow rate often creates instabilities during transitions periods in a thermostat position. These instabilities are often the result of hydrofoil effects onto plates of the thermostat that are used to fluidly block the second and third ports. These instabilities often cause the plates to vibrate or “slam” against their valve seats, thus causing damage thereto.

SUMMARY OF THE INVENTION

A thermostat assembly includes an actuator portion having a sealed container with an arm protruding therefrom. A retainer plate connects the thermostat assembly to an engine component. A bypass valve plate is arranged to sealably engage a bypass valve seat that is formed in the first engine component. The bypass valve plate includes a body portion having a central opening and an outer periphery, an inner rim surrounding the central opening, an outer rim surrounding the outer periphery, and a plurality of openings formed in the body portion. The plurality of openings are disposed adjacent to an interface between the body portion and the outer rim, such that a bypass pressure-dampening fluid passage is defined through the plurality of openings in the bypass valve plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a thermostat assembly installed between a first and second engine components.

FIG. 2 and FIG. 3 are cross-section views of one embodiment for a thermostat assembly having an improved bypass valve plate.

FIG. 4 and FIG. 5 are outline views from different perspectives of the improved bypass valve plate of the thermostat assembly shown in FIG. 2.

FIG. 6 and FIG. 7 are cross-section views of another embodiment for a thermostat assembly having an improved bypass valve plate and bypass valve seat configuration.

FIG. 8 and FIG. 9 are cross-section views of another embodiment for a thermostat assembly having an improved bypass valve plate and bypass valve seat configuration.

DESCRIPTION OF A PREFERRED EMBODIMENT

The following describes an apparatus for and method of reducing an effect of instability in cooling fluid flow through a thermostat, especially during a transitional phase of operation, by providing an improved bypass fluid flow passage that has pressure dampening characteristics.

A section view of a known thermostat 100 as installed in an internal combustion engine between a first component 102 and a second component 104 thereof is shown in FIG. 1. The thermostat 100 includes a thermal actuator assembly 106. The thermal actuator assembly 106 includes an arm 108 that is capable of extending when heated. The arm 108 passes through a cap 110 that is sealably and permanently attached to a container 112. The container 112 contains a “wax pill” 114 that melts and expands under conditions of increased temperature. A thermostat plate 115 is non-slidingly engaged with the actuator assembly 106 on an inner portion thereof, and has a seal 116 over-molded on an outer portion thereof. A retainer plate 118 surrounds a portion of the actuator assembly 106 and is disposed in a groove 120 of the second component 104.

A first spring 122 is disposed between the thermostat plate 115 and the retainer 118. The first spring 122 pushes the thermostat plate 144 away from the retainer 118. In a cold condition, the force of the first spring 122 acts to maintain a seated position of the retainer 118 in the groove 120, and to also push the thermostat plate 115 against an outlet seat 124 that is formed in the second component 104.

A bypass valve retainer 126 is connected to the actuator assembly 106 on a side thereof that is opposite the arm 108. The bypass valve retainer 126 has a bypass valve plate 128 connected to a distal end thereof. A second spring 130 is disposed between the bypass valve retainer 126 and the bypass valve plate 128, acting to push the bypass valve plate 128 away from the actuator assembly 106. In the embodiment shown, a groove 132 is formed in the first engine component 102 opposite the bypass valve plate 128. The groove 132 forms a bypass valve seat 134 that contacts the bypass valve plate 128 under certain conditions, generally, warm conditions.

During operation, a flow of coolant enters the thermostat 100. The flow of coolant, or more specifically a coolant supply from the engine, enters the thermostat 100 through an inlet opening 136. At times when the coolant flow has a lower temperature, or below about 190 degrees F. (88 degrees C.), the wax pill 114 in the actuator assembly is mostly solid, the arm 108 rests against a support 138 that is formed in the second component 104, and the bypass valve plate 128 is suspended away from the bypass valve seat 134. Thus, the coolant flow entering through the inlet opening 136 passes over the bypass valve plate 128 and exits the thermostat 100 through a bypass passage, or, a coolant return passage 140 that is formed in the first component 102 and that routs the coolant flow directly back into the engine.

When the coolant flow entering through the inlet opening 136 is warm, or has a temperature above about 190 degrees F. (88 degrees C.), the wax pill 114 melts and thermally expands within the container 112. The expansion of the wax pill 114 causes the arm 108 to extend away from the container 112, pushing against the support 138. The extension of the arm 108 causes the thermostat plate 115 to move away from the outlet seat 124, the first spring 122 to compress, and the bypass valve plate 128 to move toward the bypass valve seat 134. Continuous operation under warm conditions will eventually seat the bypass valve plate 128 onto the bypass valve seat 134. In this condition, the flow of coolant entering the inlet opening 136 will pass into an actuator chamber 142 of the thermostat 100, and exit the thermostat through a radiator outlet opening 144. The flow of coolant passing into the radiator outlet opening 144 will return to the engine after passing through a radiator (not shown).

One embodiment for an improved thermostat 200 is shown in partial cross section in FIG. 2, and in a detailed expanded cross section view in FIG. 3. The thermostat 200 has many similar features and elements with the thermostat 100, and for the sake of simplicity, common elements are called out using the same reference numerals. The thermostat 200 has an inlet opening 136, a bypass outlet opening 140, and a radiator outlet opening 144. The thermostat 200 has an improved bypass valve plate 228. The bypass valve plate 228 is connected to the bypass valve retainer 126, and functions substantially similarly to the bypass valve plate 128 shown in FIG. 1, but has a plurality of openings 230 formed along an entire periphery thereof, equidistantly from a central axis 232.

During operation of the thermostat 200, and especially during a transition period of warming coolant flow, the bypass valve plate 228 is pushed toward the bypass valve seat 134, as described. In the thermostat 100 of FIG. 1, when the bypass valve plate 128 has been pushed into the groove 132 but is not yet seated onto the bypass valve seat 134, a pressure pulsation effect is created that causes a vibration in the bypass valve plate 128. This vibration, over time, may lead to various types of failures in the bypass valve plate 128, the retainer 126, and in general, to the functionality of the thermostat 100. This vibration may advantageously be avoided with use of the improved bypass valve plate 228. The openings 230 act to relieve pressure differentials that cause the vibration across the bypass valve plate 228, and effectively eliminate the vibration and increase the service life of the thermostat 200 as compared to the service life of the thermostat 100.

An outline view from two different perspectives of the improved bypass valve plate 228 is shown in FIG. 3 and FIG. 4. The bypass valve plate 228 includes a body section 402. The body section 402 is substantially flat and has a disk shape. An outer rim 404 surrounds the body section 402 along an outer periphery thereof, and an inner rim 406 surrounds a central opening 408 of the body section 402. The outer rim 404 and the inner rim 406 advantageously provide structural stiffness to the body section 402. The plurality of openings 230 is disposed adjacent to the outer periphery of the body section 402, close to an interface between the body section 402 and the outer rim 404. The body section 402, the inner rim 404, the outer rim 406, the central opening 408, and the plurality of openings 230, may advantageously be formed simultaneously in a single stamping and cutting operation of a sheet metal piece.

During operation of the thermostat 200, a pressure dampening passage is created between the inlet opening 136, through the plurality of openings 230, through an area between the bypass valve plate 228 and the bypass valve seat 134, and out the coolant return passage 140. This pressure dampening passage is advantageously most effective at dampening pressure pulsations that would otherwise cause vibrations to the bypass valve plate at times when the bypass valve plate 228 is transitioning to a closed position and is close to and nearly seated on the bypass valve seat 134.

An alternate embodiment for a thermostat 600 having a bypass pressure-dampening fluid passage is shown in cross section in FIG. 6 and FIG. 7. The thermostat 600 has many similar features and elements with the thermostat 100, and for the sake of simplicity, common elements are called out using the same reference numerals. The thermostat 600 has an inlet opening 136, a bypass outlet opening 140, and a radiator outlet opening 144. The thermostat 600 has an improved bypass valve plate 628, and an improved bypass valve seat 634. The bypass valve plate 628 is connected to the bypass valve retainer 126, and functions substantially similarly to the bypass valve plate 128 shown in FIG. 1. The bypass valve plate 628 has an improved lateral surface 630. The lateral surface 630 has a mostly convex conical profile, and is arranged to mate with the improved bypass valve seat 634 that is formed in a first engine component 632 around an opening of the coolant return passage 140. In this embodiment, the bypass valve seat 634 has a substantially concave conical shape that matches the convex conical shape of the lateral surface 630 of the bypass valve plate 628.

During operation of the thermostat 600, and especially during a transition period of warming coolant flow, the bypass valve plate 628 is pushed toward the bypass valve seat 634, as described. The vibration described above for the thermostat 100 in FIG. 1 may advantageously be avoided with use of the improved bypass valve plate 628. The conical lateral surface 630F acts to relieve pressure differentials that cause the vibration across the bypass valve plate 628, and effectively eliminate the vibration and increase the service life of the thermostat 600 as compared to the service life of the thermostat 100.

In this embodiment, a pressure dampening passage is created between the inlet opening 136, through a passageway 636 that exists between the bypass valve plate 628 and the bypass valve seat 634, and out the coolant return passage 140. At times when the bypass valve plate 628 is near and approaching the bypass valve seat 634, a uniform flow area exists around the entire periphery of the bypass valve plate 628 in the passageway 636. The uniform flow area in the passageway 636 acts to promote efficient flow of coolant there through, and is advantageously most effective at dampening pressure pulsations that would otherwise cause vibrations to the bypass valve plate at times when the bypass valve plate 628 is transitioning to a closed position and is close to and nearly seated on the bypass valve seat 634.

An alternate embodiment for a thermostat 800 having a bypass pressure-dampening fluid passage is shown in cross section in FIG. 8 and FIG. 9. The thermostat 800 has many similar features and elements with the thermostat 100, and for the sake of simplicity, common elements are called out using the same reference numerals. The thermostat 800 has an inlet opening 136, a bypass outlet opening 140, and a radiator outlet opening 144. The thermostat 800 has an improved bypass valve plate 828, and an improved bypass valve seat 834. The bypass valve plate 828 is connected to the bypass valve retainer 126, and functions substantially similarly to the bypass valve plate 128 shown in FIG. 1.

The bypass valve plate 828 has an improved lateral surface 830. The lateral surface 830 has a mostly convex conical profile, and is arranged to linearly contact the improved bypass valve seat 834 that is formed in a first engine component 832 around an opening of the coolant return passage 140. The bypass valve seat 834 is formed as a sharp transition, at about 90 degrees, and has little to no lateral surfacing that contacts the lateral surface 830 in a flat manner. The bypass valve seat 834 can be described as a “sharp” edge surrounding the opening for the passage 140 that contacts the lateral surface 830 along a line.

During operation of the thermostat 800, and especially during a transition period of warming coolant flow, the bypass valve plate 828 is pushed toward the bypass valve seat 834, as described. The vibration described above for the thermostat 100 in FIG. 1 may advantageously be avoided with use of the improved bypass valve plate 828. The conical lateral surface 830 acts to relieve pressure differentials that cause the vibration across the bypass valve plate 828, and effectively eliminate the vibration and increase the service life of the thermostat 800 as compared to the service life of the thermostat 100.

In this embodiment, a pressure dampening passage is created between the inlet opening 136, through a passageway 836 that exists between the bypass valve plate 828 and the bypass valve seat 834, and out the coolant return passage 140. At times when the bypass valve plate 828 is near and approaching the bypass valve seat 834, a high-turbulence flow area exists around the entire periphery of the bypass valve plate 828 in the passageway 836. The flow area for fluid passing through the passageway 836 acts to destroy any pressure differentials that exist across the bypass valve plate 828 by disrupting any pressure waves with turbulence created by an edge-flow condition near the sharp transition of the seat or edge 834. This configuration is advantageously most effective at dampening pressure pulsations that would otherwise cause vibrations to the bypass valve plate at times when the bypass valve plate 828 is transitioning to a closed position and is close to and nearly seated on the bypass valve seat 834.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope. 

1. A thermostat assembly, the thermostat assembly capable of being assembled between a first engine component and a second engine component, comprising: an actuator portion that includes: a sealed container having an arm protruding therefrom, the sealed container containing a substance that expands under increased temperature conditions, a retainer plate that is capable of connecting the thermostat assembly to the second engine component, and a bypass valve retainer; a thermostat plate connected to the actuator portion, wherein the thermostat plate is arranged to sealably engage a radiator outlet seat that is formed in the second engine component; a bypass valve plate connected to the bypass valve retainer, wherein the bypass valve plate is arranged to sealably engage a bypass valve seat that is formed in the first engine component, the bypass valve plate comprising: a body portion having a central opening and an outer periphery, an inner rim surrounding the central opening, an outer rim surrounding the outer periphery, and a plurality of openings formed in the body portion, the plurality of openings disposed adjacent to an interface between the body portion and the outer rim; wherein a bypass pressure-dampening fluid passage is defined through the plurality of openings in the bypass valve plate.
 2. The thermostat assembly of claim 1, further comprising the first engine component and the second engine component.
 3. The thermostat assembly of claim 2, wherein the bypass valve seat that is formed in the first engine component is substantially flat and surrounds an outlet opening that is formed in the first engine component, and wherein the bypass pressure-dampening fluid passage includes an area between the bypass valve plate and the bypass valve seat.
 4. The thermostat assembly of claim 1, further comprising a spring disposed between the bypass valve retainer and the body portion of the bypass valve plate.
 5. The thermostat assembly of claim 1, further comprising a spring disposed between the retainer plate and the thermostat plate.
 6. The thermostat assembly of claim 1, wherein the substance in the sealed container is wax.
 7. An internal combustion engine comprising: a first component having an outlet opening formed therein; a second component having a radiator return opening in fluid communication with an actuator cavity and a retention groove, wherein the radiator return opening, the actuator cavity, and the retention groove are formed in the second component, and wherein an inlet opening that is in fluid communication with the actuator cavity is defined between the first engine component and the second engine component; a thermostat assembly that includes: an actuator assembly disposed in the actuator cavity, a retainer plate connected to the actuator assembly, wherein the retainer plate at least partially disposed in the retention groove, a thermostat valve operably connected to the actuator assembly, a bypass valve retainer operably connected to the actuator assembly, and a bypass valve plate operably associated with the bypass valve retainer, wherein the bypass valve has a lateral surface, and wherein the lateral surface has a substantially convex conical shape; wherein the first engine component forms a bypass valve seat the is in fluid communication with the outlet opening, wherein the bypass valve seat is arranged to sealably engage the bypass valve plate, and wherein a pressure-dampening fluid passage is defined from the inlet opening, through a passageway between the lateral surface of the bypass valve plate and the bypass valve seat, and the outlet opening.
 8. The internal combustion engine of claim 7, wherein the bypass valve seat has a substantially concave conical shape that is arranged to match the convex conical shape of the lateral surface.
 9. The internal combustion engine of claim 7, wherein the bypass valve seat is an edge around the outlet opening that is arranged to contact the lateral surface along a line at times when the bypass valve plate fluidly seals the outlet opening.
 10. A method for dampening fluid pressure pulsations for a thermostat comprising the steps of: passing a flow of fluid into the thermostat through an inlet opening; routing the flow of fluid to an outlet opening when a temperature of the fluid is low by sealably engaging a thermostat plate with a seat; routing the flow of fluid to a radiator outlet opening when a temperature of the fluid is high by sealably engaging a bypass valve plate with a bypass valve seat; routing the flow of fluid to both the radiator outlet opening and the outlet opening when the temperature of the fluid is between the low temperature and the high temperature; at times when the fluid temperature is approaching the hot temperature, and the bypass valve plate is approaching the bypass valve seat, providing a pressure pulsation dampening flow path between the bypass valve plate and the bypass valve seat, and passing at least a portion of the flow of fluid through the pressure pulsation dampening flow path.
 11. The method of claim 10, further comprising the step of passing at least a portion of the portion of the flow of fluid through a plurality of openings that are formed in the bypass valve plate, wherein the plurality of openings are part of the pulsation dampening flow path.
 12. The method of claim 10, wherein the pressure pulsation dampening flow path is defined between a convex conical surface that is formed on a lateral surface of the bypass valve plate and the bypass valve seat that has a concave conical shape.
 13. The method of claim 10, wherein the pressure pulsation dampening flow path is defined between a convex conical surface that is formed on a lateral surface of the bypass valve plate and the bypass valve seat that has a sharp edge transition.
 14. The method of claim 10, wherein the high temperature is any temperature above about 190 deg.F. (88 deg.C.).
 15. The method of claim 10, wherein the low temperature is any temperature below about 190 deg.F. (88 deg.C.). 